With the laws of cause and effect out the window, there naturally arises a number of inconsistencies associated with time travel, and listed here are some of those paradoxes which have given both scientist and time travel movie buffs more than a few sleepless nights over the years. The time travel paradoxes fall into two broad categories:
Predestination Paradox
The actions of a person traveling back in time becomes part of past events, and may ultimately cause the event he is trying to prevent to take place.
- This results in a ‘temporal causality loop’ in which Event 1 in the past influences Event 2 in the future (time travel to the past) which then causes Event 1 to occur, ensuring that history is not altered by the time traveler.
Solutions
The Solution: time travel is impossible because of the very paradox it creates
- Self-healing hypothesis: successfully altering events in the past will set off another set of events which will cause the present to remain the same
- the Multiverse or “many-worlds” hypothesis: an alternate parallel universe or timeline is created each time an event is altered
- Erased timeline hypothesis: a person traveling to the past would exist in the new timeline, but have their own timeline erased
Bootstrap Paradox
This is a type of paradox in which an object, person, or piece of information sent back in time results in an infinite loop where the object has no discernible origin, and exists without ever being created.
- It is also known as an Ontological Paradox, as ontology is a branch of philosophy concerned with the nature of being, or existence.
Are Self-fulfilling Prophecies Paradoxes?
Only a causality loop when the prophecy is truly known to happen and events in the future cause effects in the past
- It even works on a smaller scale – the scale of individuals
- The basic methodology for all those “self-help” books out there is that if you modify your thinking that you are successful (money, career, dating, etc.), then with the strengthening of that belief you start to behave like a successful person
Grandfather Paradox
‘Self-inconsistent solutions’ to a timeline’s history caused by traveling back in time
- Time line protection hypothesis: If you traveled to the past and killed your grandfather, you would never have been born and would not have been able to travel to the future – a paradox
- Multiple universes hypothesis: You pull the trigger and Boom! The deed is done – you return to the “present” but you never existed here
Are Time Paradoxes Inevitable?
The Butterfly Effect is a reference to Chaos Theory where seemingly trivial changes can have huge cascade reactions over long periods of time.
- Consequently, the Timeline corruption hypothesis states that time paradoxes are an unavoidable consequence of time travel, and even insignificant changes may be enough to alter history completely.
Let’s Kill Hitler Paradox
The Killing Hitler Paradox erases your own reason for going back in time to kill him.
- If you killed Hitler, then none of his actions would trickle down through history and cause you to want to make the attempt.
- Best treatment for this notion occurred in a Twilight Zone episode called Cradle of Darkness that sums up the difficulties involved in trying to change history.
Polchinski’s Paradox
This is a theoretical physicist who proposed a time paradox scenario in which a billiard ball enters a wormhole, and emerges out the other end in the past just in time to collide with its younger version and stop it going into the wormhole in the first place
- While time travel is possible, time paradoxes are forbidden
- A number of solutions have been formulated to avoid inconsistencies
